I decided it was time to build a new pack for my bike and take the old pack off to use for controller development. the battery is a few years old and still quite usable but I want more volts! The old pack is turnigy normal 5Ah 20C packs.
My new pack is being made out of the cheap 4S 5Ah hard case packs.
My first order was for 9 packs to allow for a dud but they are all good
. even after a few cycles and a resting period to detect self discharge. I ordered another to bring the total packs up to 10. The 10th pack is also looking good so far.
My plan is to build bricks two of 8S10Ah and one brick of 4S10Ah which should be quite flexible.
I just measured the self discharge from the first 9 packs that sat for well over a month at mid charge and here is the stats.
The cell numbers are across the top and the packs are the rows. All values are in delta volts
The voltage measurements were done with a single cellog.
I am unsure of the voltage calibration of the cell log but since the same channel was used both times for each cell the deltas should be good enough
There is the possibility of typos causing errors but the results look reasonably consistent apart from the one cell with zero self discharge.
My plan is to use Molex Minifit Jr connectors rather than JSTs for the balance connectors and then It becomes possible to charge through the connector at reasonable amps across the end terminals and to balance when necessary. The JST balance connectors were the worst thing with my original packs. Any poor connection and you can end up unbalancing your pack... Their pin spacing was too close for corrosion reasons when exposed to rain etc
All the parts are in so time to start building the packs
Hopefully I won't be reporting KFF or worse in the next few days